The present invention generally relates to gaskets for sealing an interface between two components.
Gaskets have long been used to seal interfaces between components in a wide variety of machines, particularly in gasoline and diesel engines. For example, head gaskets are used to create a seal between the heads of an engine and an engine block; oil pan gaskets are used to create a seal between an oil pan and an engine block; and water pump gaskets are used to create a seal around the ports of a water pump. Most gaskets are designed specifically for their particular intended use. For example, head gaskets are designed to seal against high temperatures and pressures and the generally caustic environment within the cylinders of an engine. As another example, water pump gaskets are designed to prevent the leakage of coolant, which may consist of a mixture of water and anti-freeze that is heated and under pressure.
Two performance characteristics required of most compressible gaskets are compression resistance and sealability. Compression resistance refers to the ability of a gasket to withstand high compression forces when clamped between two flange surfaces without crushing, deforming, or yielding to the point that the mechanical properties of the gasket material and ultimately the seal provided by the gasket are compromised. Sealability refers to the ability of a gasket to resist or prevent leakage of fluid both between the gasket faces and the flanges between which the gasket is clamped (referred to as “interfacial leakage”) and the ability to resist or prevent leakage of fluid through the gasket material itself (referred to as “interstitial leakage” or “bulk seal” properties).
Many different materials have been used to form gaskets. Metal gaskets traditionally have been favored because they generally have higher heat resistance, but are prone to failure in some applications due to a high level of precision needed to obtain a tight seal. In contrast, polymeric gaskets are able to conform to the surfaces more readily, but often fail over time due to chemical or physical changes in the polymer. Additionally, even prior to failure, polymeric gaskets often are perceived as failing due to oozing or creep from the sealed surfaces resulting from extrusion under pressure of the gasket. As used herein, “extrusion under pressure” refers to the radial or planar expansion or spreading of a gasket material when subject to a compression force normal to the plane of the gasket. Extrusion under pressure typically results in an undesirable permanent deformation or even destruction of the material. Thus, there is a need for an improved gasket with improved performance characteristics and sealing properties.